Answer
It sometimes happens when you use some browsers such as Internet Explorer and Opera.
These browsers incorrectly infer the file type and change the extension of the original
compressed archive file, "tar.Z" or "tar.gz", to "tar.tar".
If you use Mozilla Firefox, it does not happen.
MIME type setting of the browser seems to cause this trouble.
According to the user selected compression type, "tar+compress" or "tar+gzip",
F-net data server makes the file with the extension, "tar.Z" or "tar.gz"
If you rename "tar.tar" with the original one, you can use the downloaded file.

Answer
We are providing the moment tensor solutions through the following page.
http://www.fnet.bosai.go.jp/event/search.php?LANG=en
In this page you will be able to get the moment tensors by specifying several parameters to
select your favarite earthquakes. HTML, TEXT, and GMT are available as output data format.

Answer
You can get the response file at
here
in order to correct the instrumental response.
You will find the instruction for this file at
http://www.fdsn.org/seed_manual/SEEDManual_V2.4.pdf
or you may get the SEED format data file which includes the instrumental response in its header.
The SEED format instruction is also find in SEEDManual_V2.4.pdf located above.

Answer
NZMSEC is the observed value.
Since at each station time is syncronized by the GPS clock and the digital filter is used,
the time at each sample is not a round value. However, sampling interval is accurate.
So in the header, the time in micro-seconds of the first data sample is shown.
At present you cannot specify the time window in mili-seconds for the request of data retrieval.

Answer
We would appologize that we did not update the page you pointed out for a long time.
We now updated the page including new information as well as reflecting your suggestion.
Please visit the following
page
again.

Answer
We have been analyzing the earthquakes whose magnitude is greater than 3.5 based on the
Emergent hypocenter information by JMA (Japan Meteorological Agency)
as well as on the Unifyed hypocenter catalog maintained by JMA.
However, we do not show all the result but the earthquakes whose variance reduction
(an index to measure the fit between observation and synthetics, 100% means perfect fit)
is greater than 50% are shown in the catalog.
Generally speaking, most of M4 earthquakes will be included.
But during the swarm activity or after the huge earthquake at teleseismic distance,
the waveforms are contaminated and it becomes difficult to analyse the waveforms.
Thus these earthquakes are dropped in the catalog. Unfortunately we did not conduct the statistical
analysis on this matter, so that we could only say the qualitative answer at this time.
As for the reference of the moment tensor analysis, please refer to the following paper:

Answer
It is not same to intensity scale of US. And it is also not same to Richter scale.
The intensity scale is decided from body sensation and actions of things when earthquake occurs.
You can see more details in JMA homepage.http://www.jma.go.jp/jma/kishou/know/shindo/explane.html